The invention relates to water bath separator for separating floating material from material that sinks when deposited in a water bath.
A known application of water bath separators is in the field of sorting construction and demolition waste. Depositing construction and demolition waste in a landfill is expensive. Recycling of potentially re-usable constituents of the waste replaces the costs of disposing a usable or re-usable fraction of the waste by the creation of value of the usable or re-usable materials obtained thereby create a value and contributes to reducing the consumption of natural resources.
Construction and demolition waste is preferably first sized to present only clean, large items on an “covers” sort line. The “unders” line can screen out a product as fine as sand and have the balance cleaned up with an air system, for instance such that a stream of particles mainly having sizes in a range between 1 cm and 2.5 cm is obtained. A water-bath separator is preferably used after that for separating a flotsam fraction from a jetsam fraction of the “unders” or the “covers” material. The sorting may also be carried out in another order, with other size ranges or even only to sort floating particles from sinking particles.
The material to be separated is fed to the water bath and a water flow is maintained in the water bath that entrains the floating fraction to a conveyor that picks up the floating material out of the water bath towards a vibrating screen where water that loosely clings to the material is separated from the material.
The heavier material is transported by an incline conveyor from a lower portion of the water bath to a granulate bunker, or can be send over a quality control sorting line, for the final check for materials, such as PVC.
A problem of water bath separators is that particles of the light fraction of the materials to be sorted are not always quickly engaged by the conveyor for removal from the water bath. In particular, particles that float deeply, such as materials having a specific weight close to the specific weight of water, such as tropical wood or particles having a particular shape, sometimes remain at the upstream end of the discharge conveyor before being entrained out of the water bath.